School of Aging Studies Professor Ross Andel weighed in on a perplexing issue recently on Gizmodo, a website devoted to design, technology, and science.

Why do our faces change shape as we get older?

It's not a superficial issue.

It’s all about our bones, he wrote, and connective tissues.

“Bones, in particular, are quite dynamic. Over time, they do not rebuild themselves as well, leading to overall reduction in mass, which can lead to differences in the shape of face. Eye sockets enlarge and lower jaw decreases in length and height. Connective tissue in the nose and some changes in the angle make the nose appear larger.”

The molecules of the skin share some of the blame, too. Through a process called cross-linking, the bonding across collagen and elastin molecules becomes less flexible, more rigid.

If this makes you want to grimace, don’t. Continuous contracting of the muscles during concentration or stress only makes wrinkles look deeper over time.

Dr. Andel was one of several scientists to address the question for Gizomodo’s “Giz Asks.”